All the components that are voltaged in at least one operating state of the switching device can be understood to be voltaged components. However, they need not actually be voltaged in every operating state of the switching device. Depending upon its setting, for example, a switch is not always voltaged, even though by means of a switching process it can be translated into an operating state in which it is voltaged.
Depending upon the definitions used the demarcations of the regions of medium, high or extremely high voltage can vary. According to one prevalent definition, the medium voltage region extends from 1 kV to 52 kV and the high-voltage region from 52 kV to 110 kV. According to another definition the high-voltage region starts earlier at 50 kV. Voltages greater than 110 kV are designated as extremely high voltages. Accordingly a switching device for medium, high or extremely high voltage can be understood to be a switching device for voltages from 1 kV upwards.
Switchgear and switching equipment for medium, high or extremely high-voltage are also included amongst these switching devices. A multiplicity of switching devices of this type are of known prior art.
An exemplary item of switching equipment for medium, high or extremely high voltage is a switch for voltages such as are also used, for example, in switchgear for medium, high or extremely high voltage. Switchgear of this type allow, by means of appropriate switching the formation of connections between different conductors, and thus, for example, the supply of energy to various consumers, or the reaction to failures of particular conducting paths, in that these are bridged by the selection of alternative energy supply paths.
Switching devices for medium, high or extremely high voltage must often satisfy high requirements with respect to their reliability and human safety. These include, for example, in switches for medium, high or extremely high-voltage, such as power switches, power disconnectors, load switches, circuit breakers, load disconnectors, etc., the requirement that arcs occurring between the contacts during the switching processes can be rapidly extinguished, or that their occurrence can be prevented. To satisfy these requirements various solutions have been proposed in the past. Thus switches for medium, high or extremely high voltages can be assigned extinguishing coils that have the task of extinguishing switching arcs. Likewise voltaged components of switching devices for medium, high or extremely high voltage can be enclosed in an enclosure that is filled with a filling medium. As an example it should be stated here that the contacts of switches for medium, high or extremely high voltage are often enclosed in an enclosure that is filled with a filling medium. The filling medium can have the property of rapidly extinguishing any arcs that occur, i.e. it can act as an arc extinguishing medium.
Voltaged components of switchgear for medium, high or extremely high voltage, for example, busbars, can be enclosed in an enclosure that can, for example, be designed as a separate chamber or bulkhead compartment in the housing of the switchgear. A suitable filling medium with which this enclosure is filled can act as an electrical insulation medium and can insulate voltaged components from other components of the switchgear. Equally it can act as an arc extinguishing medium for any fault arcs that may occur within the switchgear. The personal safety of operators of the switchgear can be increased both by means of an electrical insulation action of a filling medium and also by means of a fault arc extinguishing action of a filling medium. If fault arcs are extinguished promptly after they appear down times and maintenance requirements can be reduced. Instead of filling with a filling medium a vacuum is also often generated in the enclosure of switching devices for medium, high or extremely high voltage.
Air, oil and a “solid gas”, i.e. a material that translates into a gaseous state only when the arc develops can be named as filling media, amongst others. DE 598 450 A discloses a circuit breaker. The breaker contacts of the circuit breaker are accommodated in containers filled with oil. From DE 641 963 A a metal-clad electrical switchgear is of known art, in which components such as a power switch and a transformer are accommodated in a vessel filled with oil as an insulation fluid.
However, sulphur hexafluoride (SF6) is also often used as a filling medium that is suitable both as an arc extinguishing medium and also as an electrical insulation medium. In comparison to air SF6 offers the advantage of a higher breakdown resistance by a factor of approximately 2.5 at standard pressure. This makes possible small insulation separation distances, and thus allows the design of more compact switching devices for medium, high or extremely high-voltage. From DE 195 19 301 A1 a breaker for a metal-enclosed gas-insulated high-voltage switchgear is of known art. Here a contact pin and an opposing contact are arranged in a housing that is filled with SF6 as an insulation gas. DE 32 15 234 C2 describes enclosed medium voltage switchgear, in which switching blades are arranged in a housing filled with an insulation gas; the blades can be brought into three switching positions.
From the point of view of environmental protection, and in particular climate protection, however, SF6 is beset with many disadvantages. Its global warming potential (GWP), also known as its CO2-equivalent, is 22,800. Thus 1 kg of SF6 over a time period of 100 years is considered to be just as damaging as 22,800 kg of CO2. Moreover its atmospheric lifespan is extremely high at 3200 years. Thus in Europe, for example, the handling and use of SF6 is subject to stringent regulations. Stocks of SF6 and its consumption must be monitored, for example.